Featured Research

Exploding Frog Eggs And People With Rare Disorder Help Researchers Unravel Mysteries Of Water Regulation In Humans: Discovery May Lead To Treatments For Kidney Disorders

Date:

August 15, 2001

Source:

Johns Hopkins Medical Institutions

Summary:

Acting on a scientific hunch, Hopkins medical sleuths set out to find individuals with an extremely rare disorder affecting their ability to internally process water. Using international blood banks, the investigators identified two such persons, confirming their belief that the absence of a certain protein interferes with the body’s ability to regulate its water levels.

Share This

Acting on a scientific hunch, Hopkins medical sleuths set out to find individuals with an extremely rare disorder affecting their ability to internally process water. Using international blood banks, the investigators identified two such persons, confirming their belief that the absence of a certain protein interferes with the body’s ability to regulate its water levels. The finding, reported in the July 19 issue of the New England Journal of Medicine, provides insight into how the kidney works.

Related Articles

"This is the first study to show that the protein called aquaporin-1 has a clear role in the normal function of the kidney," says Landon King, M.D., an assistant professor of pulmonary medicine and lead author of the study. "Aquaporin-1 is required for the kidney to concentrate urine, a fundamental process for all mammals."

The study showed that individuals deficient in the protein have a limited ability to concentrate urine, or, in other words, to reabsorb water through their kidneys. This is essential for maintaining healthy water levels in the body. The finding may help doctors develop treatments for diseases such as diabetes insipidus, an ailment that inhibits reabsorption of water causing frequent urination and emaciation.

Until 10 years ago, scientists didn’t know how cells regulate water, surprising since this task is fundamental to life. Water makes up 70 percent of the human body, and while certain cells need to absorb water quickly, other cells are relatively impermeable to water. Then, roughly 10 years ago, Peter Agre, M.D., a Hopkins professor of biochemistry, stumbled upon an unknown protein lodged in the plasma membrane of red blood cells and kidney tubules. After expressing the protein in frogs’ eggs, the scientists discovered that the eggs exploded when immersed in water because they absorbed the liquid much faster than normal. Agre named the protein aquaporin because it acted as a pore or water channel through which fluids flow in and out of the membrane.

Since the exploding frog eggs, scientists have identified 10 aquaporin proteins in the more water-permeable parts of the body -- the moist surface tissues of the alveoli in the lung, tubules in the kidneys, and tear glands, to name a few. But researchers wondered whether they could find any people with missing or defective aquaporin proteins. To accomplish their goal, Agre and pulmonologist Landon King turned to international blood banks and identified six families with a deficiency in aquaporin-1(AQP1). After tracking down two of the individuals – a 37-year-old woman from North Carolina and a 57-year old woman from France – and depriving them of water for 24 hours under close monitoring, King determined that they have a limited ability to concentrate urine.

Surprisingly however, the individuals did not have more serious health issues, since AQP1 is involved in transporting water not only in the kidneys but in a number of other organs, including the lungs and pancreas. "We believe that these people have some form of compensation that helps to mitigate the severity of the problem and most likely developed these compensatory mechanisms in the womb," says King. "If a person suddenly developed a deficiency in AQP1 without these compensatory mechanisms, they are much more likely to have severe health problems."

In addition to King and Agre, other authors include Michael Choi, M.D., from Johns Hopkins, as well as Jean-Pierre Cartron, Ph.D., and Pedro Fernandez, M.D., from the University of Pennsylvania. The National Institutes of Health, the Cystic Fibrosis Foundation and the National Center for Research Sources funded the study.

Johns Hopkins Medical Institutions. "Exploding Frog Eggs And People With Rare Disorder Help Researchers Unravel Mysteries Of Water Regulation In Humans: Discovery May Lead To Treatments For Kidney Disorders." ScienceDaily. ScienceDaily, 15 August 2001. <www.sciencedaily.com/releases/2001/08/010815082342.htm>.

Johns Hopkins Medical Institutions. (2001, August 15). Exploding Frog Eggs And People With Rare Disorder Help Researchers Unravel Mysteries Of Water Regulation In Humans: Discovery May Lead To Treatments For Kidney Disorders. ScienceDaily. Retrieved March 3, 2015 from www.sciencedaily.com/releases/2001/08/010815082342.htm

Johns Hopkins Medical Institutions. "Exploding Frog Eggs And People With Rare Disorder Help Researchers Unravel Mysteries Of Water Regulation In Humans: Discovery May Lead To Treatments For Kidney Disorders." ScienceDaily. www.sciencedaily.com/releases/2001/08/010815082342.htm (accessed March 3, 2015).

More From ScienceDaily

More Health & Medicine News

Featured Research

Mar. 3, 2015 — New assays can detect malaria parasites in human blood at very low levels and might be helpful in the campaign to eradicate malaria, reports a new study. An international team led by Ingrid Felger, ... full story

Mar. 3, 2015 — Adults over the age of 30 only catch flu about twice a decade, a new study suggests. So, while it may feel like more, flu-like illness can be caused by many pathogens, making it difficult to assess ... full story

Mar. 3, 2015 — No significant change in home habits of smokers have been observed in the aftermath of a ban on smoking in public spaces, researchers report. Greater inspiration to kick the habit likely comes from ... full story

Mar. 3, 2015 — Heart function has been associated with the development of dementia and Alzheimer's disease through a new study. Participants with decreased heart function, measured by cardiac index, were two to ... full story

Mar. 3, 2015 — Children of recently separated or divorced families are likelier to drink sugar-sweetened beverages than children in families where the parents are married, putting them at higher risk for obesity ... full story

Mar. 3, 2015 — Gastric bypass and similar stomach-shrinking surgeries are a popular option for obese patients looking to lose weight or treat type 2 diabetes. While the surgeries have been linked to a decreased ... full story

Mar. 3, 2015 — Most people consume more salt than they need and therefore have a higher risk of heart disease and stroke, which are the two leading causes of death worldwide. But a new study reveals that dietary ... full story

Mar. 3, 2015 — Twice as many children born to mothers who took antibiotics during pregnancy were diagnosed with asthma by age 3 than children born to mothers who didn’t take prenatal antibiotics, a new study has ... full story

Mar. 3, 2015 — Although sedatives are often administered before surgery, a randomized trial finds that among patients undergoing elective surgery under general anesthesia, receiving the sedative lorazepam before ... full story

Featured Videos

Mom Triumphs Over Tragedy, Helps Other Families

AP (Mar. 3, 2015) — After her son, Dax, died from a rare form of leukemia, Julie Locke decided to give back to the doctors at St. Jude Children&apos;s Research Hospital who tried to save his life. She raised $1.6M to help other patients and their families. (March 3)
Video provided by AP

Looted and Leaking, South Sudan's Oil Wells Pose Health Risk

AFP (Mar. 3, 2015) — Thick black puddles and a looted, leaking ruin are all that remain of the Thar Jath oil treatment facility, once a crucial part of South Sudan&apos;s mainstay industry. Duration: 01:13
Video provided by AFP

Woman Convicted of Poisoning Son

AP (Mar. 3, 2015) — A woman who blogged for years about her son&apos;s constant health woes was convicted Monday of poisoning him to death by force-feeding heavy concentrations of sodium through his stomach tube. (March 3)
Video provided by AP

Feb. 26, 2012 — Researchers have identified an elusive gene responsible for Thrombocytopenia with Absent Radii (TAR), a rare inherited blood and skeletal disorder. As a result, this research is now being transformed ... full story

Oct. 24, 2011 — Age-related macular degeneration (AMD) is the leading cause of severe visual loss among the elderly. Researchers had previously identified several relatively common genetic variants which together ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.